I've finally done the passive mod on my 7520. The only mod it had was a THS4032 opamp. For capacitors I used Obbligato 1uF, these capacitors are well used so burn-in really isn't needed. Transport is XP/Foobar/ASIO/USB.

The effect was very dramatic. Sound stage is much deeper, there's more bass and the bass is tighter. Treble is less splashy. Overall it sounds a heck of a lot less digital and more like my record decks, especially with regard to sound stage depth.

Hmmm, Wolfson next I suppose.